Lab 5. Tensile Test of Composites

Question 1

some of the factors that determine material selection are:

Answer 1

Some of the factors that determine material selection are:

Application – structural, aesthetic, electrical etc.

Working conditions – loads, temp, pressure etc.

Availability

Cost

Ease of manufacturing

Service life

Question 2

Composite materials

Answer 2

can be defined as materials consisting of two or more constituents (phases) that are combined at the macroscopic level and are not soluble in each other.

Question 3

There are many natural occurring composites such as?

Answer 3

wood and bone

Question 4

wood

Answer 4

consists of strong cellulose fibers held together by a liguin matrix

Question 5

bones

Answer 5

consists of short and soft collagen fibers embedded in a mineral matrix

Question 6

A material can be called a composite when….

Answer 6

The constituents are non-soluble

The constituents have a recognizable interface between them
The constituents differ in physical and chemical form

It has characteristics that are not depicted by any of the components in isolation

Question 7

what are the two phases of a composite and describe how they correlate

Answer 7

matrix (continuous) bulk phase

and reinforcement (non continuous) usually harder and stronger.

bulk phase accepts the load over a large surface area,
transfers it to the reinforcement, which being stiffer, increases the strength of the composite.

Question 8

how can composites be reinforced?

Answer 8

particle reinforced, fiber reinforced, structural reinforced

Question 9

name some matrix materials (bluk phase)

Answer 9

Polymers
Metals
Ceramics

Question 10

name some reinforcements : fibers and particulates

Answer 10

Glass 
Carbon 
Organic 
Boron 
Ceramic 
Metallic

Question 11

it is very important to have good _____ between phases

Answer 11

interfacial bonding

Question 12

metal matrix composites have ______ and ____ exmples

Answer 12

strength and toughness…

aluminium or titanium alloys

Question 13

ceramic composites have high ______ examples?

Answer 13

thermal stability

alumina

Question 14

Polymer matrix composite- is the

they are usually reinforced with____

Answer 14

most widely used composite

they are low in price and processing ; having a range of molecular configurations give rise to multitude rage of of properties

glass, carbon and aramid fibers

Question 15

applications of composites

Answer 15

aerospace, aircraft, chemical construction, domestic electrical leisure, marine medical transportation

Question 16

what is the roll of the matrix

Answer 16

transfer load to reinforcement

protect the reinforcement…

provide solid form

bind reinforcement

Question 17

role of reinforcement

Answer 17

provide strength
increase toughness

provide framework for adhesion
enhance electrical/thermal properties

Question 18

materials are formed into layers called

Answer 18

lamina

Question 19

strength and other properties are largely dependent on

Answer 19

The arrangement or orientation of the fibers relative to one another
The fiber concentration
The distribution
Amount of defect

Question 20

composite have _______ and ______ compared to metals

Answer 20

higher specific strength and higher specific stiffness

Question 21

Advantages:

Answer 21

High mechanical properties
Flexibility of design options
Ease of fabrication
Light weight
Environmental durability
Impact resistance
Excellent fatigue strength

Question 22

disadvantages

Answer 22

High material cost
High manufacturing cost
Temperature limitations
Brittle failure mechanism
Actual mechanical properties not always as good as expected
Mechanical properties are process dependent